Is there any way to replicate/recreate Levels effect in Blender Shading Nodes?
You can get the same functionality with the Color Ramp node.

Add > Converter > Color Ramp



And because the Color Ramp node uses 0-1 value range, just multiply your value by 1 / 255.
Like this:  



You can technically also do this with RGB curves, they're just a different tool for doing the same thing.